1. Field of the Invention
The present invention relates to a video signal noise reduction circuit for use in a video tape recorder, a video movie, and the like.
2. Description of the Related Art
In a video tape recorder, as shown in FIG. 1, a picture quality control circuit 51 is connected to a noise canceller circuit 52 in the succeeding stage. A regenerative video signal is input to the noise canceller circuit 52. The picture quality control circuit 51 adjusts the frequency characteristic of the video signal under the control of an external controller 53, thereby controlling the quality of a picture. A gain for the video signal is usually controlled in a certain bandwidth by the external controller 53. The noise canceller circuit 52 regards a video signal at a level lower than a predetermined level (limiter level) as a noise component, and extracts a noise component from the video signal to cancel the noise component.
The noise canceller circuit 52 is not ordinarily designed to delete the noise component completely, and a minute noise component is often left. For example, it reduces the noise component to -10 dB level. Therefore, if the picture quality control circuit 51 is connected to the noise canceller circuit 52 in the succeeding stage, the minute noise component which has been without being cancelled are amplified by the picture quality control circuit 51 and impair the picture quality. Furthermore, even if another noise canceller circuit (not shown) similar to the noise canceller circuit 52 is connected to the output of the picture quality control circuit 51, the conventional noise canceller circuit 52, which has above fixed limiter level, performs but incomplete cancellation of the noise component. This is because the level of the noise component included in the video signal should be changed according to the gain control of the picture quality control circuit 51.